As described in German patent 2,603,986 filed Feb. 3, 1976, a machine of the type used for long-wall mining of coal has a conveyor to one side of which is secured a guide-rail assembly on which rides a mining machine that scrapes coal or ore from the face from which the coal or ore is being recovered. The guide-rail assembly forms an upwardly open cruciform-section passage in which is received a longitudinally displaceable round-link drive chain. The mining machine has a toothed wheel rotatable about a horizontal axis and positioned so its teeth can engage in the holes of the horizontal links of the chain, in effect using it like a rack.
The passage is formed by a plurality of metal bars that are bolted together to the conveyor so that the horizontal links are held relatively snugly, with limited ability to move relative to the rail assembly while the vertical links have substantial freedom of movement in the guide passage.
Such an assembly is subjected to enormous wear from the great forces being applied to it and the gritty and dirty environment is used in. In order to repair or work on the guide rail it is necessary to largely dismantle the conveyor. This is difficult and time-consuming, entailing substantial down time for the apparatus when it needs service.